Altas Farnese
... suggesting a date of c. 128 A.D. Third, art historians all point to the original Greek sculptor as using the constellations based in Aratus’s poem Phaenomena, which has a date of c. 275 B.C. An origin with Aratus was the dominant opinion amongst scholarly publications in the last century. Fourth, we ...
... suggesting a date of c. 128 A.D. Third, art historians all point to the original Greek sculptor as using the constellations based in Aratus’s poem Phaenomena, which has a date of c. 275 B.C. An origin with Aratus was the dominant opinion amongst scholarly publications in the last century. Fourth, we ...
Type Ia supernovae as stellar endpoints and cosmological tools
... because dark energy is so dilute (1 m3 contains the energy equivalent to a few atoms of hydrogen), its effects can only be seen on vast scales. We must compare supernovae across ~10 Gyr of cosmic time, during which stars and galaxies have undergone substantial evolution. Therefore, it is critical to ...
... because dark energy is so dilute (1 m3 contains the energy equivalent to a few atoms of hydrogen), its effects can only be seen on vast scales. We must compare supernovae across ~10 Gyr of cosmic time, during which stars and galaxies have undergone substantial evolution. Therefore, it is critical to ...
Multiplicity in Early Stellar Evolution - Astronomy Group
... discussed in section 2. However, most protostars are still deeply embedded, so such observations are hampered by extinctions that can exceed AV ~ 100 mag. Hence infrared, submillimeter, or radio continuum observations are required. 4.1. Infrared Observations Class I protostars are often detectable ...
... discussed in section 2. However, most protostars are still deeply embedded, so such observations are hampered by extinctions that can exceed AV ~ 100 mag. Hence infrared, submillimeter, or radio continuum observations are required. 4.1. Infrared Observations Class I protostars are often detectable ...
Spacecraft Navigation Using X-Ray Pulsars
... on their collapse stars with insufficient mass to create a black hole produce several types of ultradense, compact objects.6,7 One such proposed object is a neutron star (NS).8−10 This object is the result of a massive star that has exhausted its nuclear fuel and undergone a core collapse resulting ...
... on their collapse stars with insufficient mass to create a black hole produce several types of ultradense, compact objects.6,7 One such proposed object is a neutron star (NS).8−10 This object is the result of a massive star that has exhausted its nuclear fuel and undergone a core collapse resulting ...
X-Ray Spectroscopy of Stars
... stars located across almost all regions of a Hertzsprung-Russell diagram have been identified as X-ray sources, with only a few exceptions, most notably A-type stars and the coolest giants of spectral type M. But even for those two classes, important exceptions exist. X-rays have been identified fro ...
... stars located across almost all regions of a Hertzsprung-Russell diagram have been identified as X-ray sources, with only a few exceptions, most notably A-type stars and the coolest giants of spectral type M. But even for those two classes, important exceptions exist. X-rays have been identified fro ...
Lichtenknecker- Database of the BAV
... 13mag during maximum light and a declination north of –20 degree. There is no limit regarding the amplitude of the change of light or period. Due to the increasing use of CCD-cameras in the recent years also fainter objects were included into the database if more than one minimum was published. For ...
... 13mag during maximum light and a declination north of –20 degree. There is no limit regarding the amplitude of the change of light or period. Due to the increasing use of CCD-cameras in the recent years also fainter objects were included into the database if more than one minimum was published. For ...
CoRoT III programme
... time. Oscillation modes have been measured down to the ppm (part-per-million) level for stars with intermediate (~2Msun) to very high (~45 Msun) mass, revealing phenomena hitherto out of reach. Seismology of Red Giants really started with CoRoT and is now one of the most promising and active fields ...
... time. Oscillation modes have been measured down to the ppm (part-per-million) level for stars with intermediate (~2Msun) to very high (~45 Msun) mass, revealing phenomena hitherto out of reach. Seismology of Red Giants really started with CoRoT and is now one of the most promising and active fields ...
The size of AB Doradus A from VLTI/AMBER interferometry⋆
... below) and two additional exposures for dark and flat correction, each exposure having 200 frames, each recorded with a DIT of 50 milliseconds. Target and calibrator were observed alternatively. To ensure a proper amplitude calibration, we used three different calibrators, namely HD 35199, HD 39608, ...
... below) and two additional exposures for dark and flat correction, each exposure having 200 frames, each recorded with a DIT of 50 milliseconds. Target and calibrator were observed alternatively. To ensure a proper amplitude calibration, we used three different calibrators, namely HD 35199, HD 39608, ...
Observations, Modeling and Theory of Debris Disks
... Universidad Autónoma de Madrid Main sequence stars, like the Sun, are often found to be orbited by circumstellar material that can be categorized into two groups, planets and debris. The latter is made up of asteroids and comets, as well as the dust and gas derived from them, which makes debris dis ...
... Universidad Autónoma de Madrid Main sequence stars, like the Sun, are often found to be orbited by circumstellar material that can be categorized into two groups, planets and debris. The latter is made up of asteroids and comets, as well as the dust and gas derived from them, which makes debris dis ...
Observations, Modeling and Theory of Debris Disks
... Universidad Autónoma de Madrid Main sequence stars, like the Sun, are often found to be orbited by circumstellar material that can be categorized into two groups, planets and debris. The latter is made up of asteroids and comets, as well as the dust and gas derived from them, which makes debris dis ...
... Universidad Autónoma de Madrid Main sequence stars, like the Sun, are often found to be orbited by circumstellar material that can be categorized into two groups, planets and debris. The latter is made up of asteroids and comets, as well as the dust and gas derived from them, which makes debris dis ...
Annual Report 2010 - Koninklijke Sterrenwacht van België
... (3) It was shown that using GNSS data from national densification networks in addition to the EPN provides an added-value for tropospheric tomography. In the case of ionospheric tomography, the additional stations induce inhomogeneities in the GNSS signal distribution and therefore mainly densifica ...
... (3) It was shown that using GNSS data from national densification networks in addition to the EPN provides an added-value for tropospheric tomography. In the case of ionospheric tomography, the additional stations induce inhomogeneities in the GNSS signal distribution and therefore mainly densifica ...
Differential rotation on both components of the pre-main
... 3 C O M PA R I N G I N D E P E N D E N T M A P S The 1.68 d orbital period of HD 155555 allows us to obtain full phase coverage in five nights. Given that we have a total time-base of 11 nights (March 30–April 09), we can therefore create two entirely independent maps of both components of HD 155555 ...
... 3 C O M PA R I N G I N D E P E N D E N T M A P S The 1.68 d orbital period of HD 155555 allows us to obtain full phase coverage in five nights. Given that we have a total time-base of 11 nights (March 30–April 09), we can therefore create two entirely independent maps of both components of HD 155555 ...
Here - NASA/IPAC Extragalactic Database
... Planetary nebulae (PNe) are evolutionary products of so-called intermediate mass stars (initial masses of 1 – 8 M ) as they progress from the asymptotic giant branch (AGB) to the white dwarf stage. It is the interaction of the slow AGB wind with the fast post-AGB wind which produces the nebula. Bec ...
... Planetary nebulae (PNe) are evolutionary products of so-called intermediate mass stars (initial masses of 1 – 8 M ) as they progress from the asymptotic giant branch (AGB) to the white dwarf stage. It is the interaction of the slow AGB wind with the fast post-AGB wind which produces the nebula. Bec ...
THE OFFSET AND HOST LIGHT DISTRIBUTIONS OF LONG
... hosts, and (ii) measuring the fractional brightness at the LGRB positions relative to the overall distribution of light within their hosts. In this context, Bloom et al. (2002) combined groundbased afterglow observations and Hubble Space Telescope (HST) host observations to measure the offsets of 20 ...
... hosts, and (ii) measuring the fractional brightness at the LGRB positions relative to the overall distribution of light within their hosts. In this context, Bloom et al. (2002) combined groundbased afterglow observations and Hubble Space Telescope (HST) host observations to measure the offsets of 20 ...
Understanding Variable Stars - Central Florida Astronomical Society
... Understanding Variable Stars Variable stars are those that change brightness. Their variability may be due to geometric processes such as rotation, or eclipse by a companion star, or physical processes such as vibration, flares, or cataclysmic explosions. In each case, variable stars provide unique ...
... Understanding Variable Stars Variable stars are those that change brightness. Their variability may be due to geometric processes such as rotation, or eclipse by a companion star, or physical processes such as vibration, flares, or cataclysmic explosions. In each case, variable stars provide unique ...
Combined Earth-/Star-Sensor for Attitude and Orbit Determination of
... The subject of this work is a sensor for autonomous attitude and orbit determination of satellites, based on active pixel technology as it has been proposed in the patent on a „Combined Earth-/ Star-Sensor System and Method for Determining the Orbit and Position of Spacecraft“ developed at Daimler-C ...
... The subject of this work is a sensor for autonomous attitude and orbit determination of satellites, based on active pixel technology as it has been proposed in the patent on a „Combined Earth-/ Star-Sensor System and Method for Determining the Orbit and Position of Spacecraft“ developed at Daimler-C ...
User`s Manual for DAOPHOT II This manual is intended as a guide
... (5) A principal source of photometric error for the faint stars is the difficulty of defining what is meant by the term “sky brightness” in crowded fields. This is not simply the practical difficulty of identifying “contaminated” pixels in the sky annulus so that they can be omitted from the average ...
... (5) A principal source of photometric error for the faint stars is the difficulty of defining what is meant by the term “sky brightness” in crowded fields. This is not simply the practical difficulty of identifying “contaminated” pixels in the sky annulus so that they can be omitted from the average ...
Observational astronomy
Observational astronomy is a division of the astronomical science that is concerned with recording data, in contrast with theoretical astrophysics, which is mainly concerned with finding out the measurable implications of physical models. It is the practice of observing celestial objects by using telescopes and other astronomical apparatus.As a science, the study of astronomy is somewhat hindered in that direct experiments with the properties of the distant universe are not possible. However, this is partly compensated by the fact that astronomers have a vast number of visible examples of stellar phenomena that can be examined. This allows for observational data to be plotted on graphs, and general trends recorded. Nearby examples of specific phenomena, such as variable stars, can then be used to infer the behavior of more distant representatives. Those distant yardsticks can then be employed to measure other phenomena in that neighborhood, including the distance to a galaxy.Galileo Galilei turned a telescope to the heavens and recorded what he saw. Since that time, observational astronomy has made steady advances with each improvement in telescope technology.A traditional division of observational astronomy is given by the region of the electromagnetic spectrum observed: Optical astronomy is the part of astronomy that uses optical components (mirrors, lenses and solid-state detectors) to observe light from near infrared to near ultraviolet wavelengths. Visible-light astronomy (using wavelengths that can be detected with the eyes, about 400 - 700 nm) falls in the middle of this range. Infrared astronomy deals with the detection and analysis of infrared radiation (this typically refers to wavelengths longer than the detection limit of silicon solid-state detectors, about 1 μm wavelength). The most common tool is the reflecting telescope but with a detector sensitive to infrared wavelengths. Space telescopes are used at certain wavelengths where the atmosphere is opaque, or to eliminate noise (thermal radiation from the atmosphere). Radio astronomy detects radiation of millimetre to dekametre wavelength. The receivers are similar to those used in radio broadcast transmission but much more sensitive. See also Radio telescopes. High-energy astronomy includes X-ray astronomy, gamma-ray astronomy, and extreme UV astronomy, as well as studies of neutrinos and cosmic rays.Optical and radio astronomy can be performed with ground-based observatories, because the atmosphere is relatively transparent at the wavelengths being detected. Observatories are usually located at high altitudes so as to minimise the absorption and distortion caused by the Earth's atmosphere. Some wavelengths of infrared light are heavily absorbed by water vapor, so many infrared observatories are located in dry places at high altitude, or in space.The atmosphere is opaque at the wavelengths used by X-ray astronomy, gamma-ray astronomy, UV astronomy and (except for a few wavelength ""windows"") far infrared astronomy, so observations must be carried out mostly from balloons or space observatories. Powerful gamma rays can, however be detected by the large air showers they produce, and the study of cosmic rays is a rapidly expanding branch of astronomy.For much of the history of observational astronomy, almost all observation was performed in the visual spectrum with optical telescopes. While the Earth's atmosphere is relatively transparent in this portion of the electromagnetic spectrum, most telescope work is still dependent on seeing conditions and air transparency, and is generally restricted to the night time. The seeing conditions depend on the turbulence and thermal variations in the air. Locations that are frequently cloudy or suffer from atmospheric turbulence limit the resolution of observations. Likewise the presence of the full Moon can brighten up the sky with scattered light, hindering observation of faint objects.For observation purposes, the optimal location for an optical telescope is undoubtedly in outer space. There the telescope can make observations without being affected by the atmosphere. However, at present it remains costly to lift telescopes into orbit. Thus the next best locations are certain mountain peaks that have a high number of cloudless days and generally possess good atmospheric conditions (with good seeing conditions). The peaks of the islands of Mauna Kea, Hawaii and La Palma possess these properties, as to a lesser extent do inland sites such as Llano de Chajnantor, Paranal, Cerro Tololo and La Silla in Chile. These observatory locations have attracted an assemblage of powerful telescopes, totalling many billion US dollars of investment.The darkness of the night sky is an important factor in optical astronomy. With the size of cities and human populated areas ever expanding, the amount of artificial light at night has also increased. These artificial lights produce a diffuse background illumination that makes observation of faint astronomical features very difficult without special filters. In a few locations such as the state of Arizona and in the United Kingdom, this has led to campaigns for the reduction of light pollution. The use of hoods around street lights not only improves the amount of light directed toward the ground, but also helps reduce the light directed toward the sky.Atmospheric effects (astronomical seeing) can severely hinder the resolution of a telescope. Without some means of correcting for the blurring effect of the shifting atmosphere, telescopes larger than about 15–20 cm in aperture can not achieve their theoretical resolution at visible wavelengths. As a result, the primary benefit of using very large telescopes has been the improved light-gathering capability, allowing very faint magnitudes to be observed. However the resolution handicap has begun to be overcome by adaptive optics, speckle imaging and interferometric imaging, as well as the use of space telescopes.Astronomers have a number of observational tools that they can use to make measurements of the heavens. For objects that are relatively close to the Sun and Earth, direct and very precise position measurements can be made against a more distant (and thereby nearly stationary) background. Early observations of this nature were used to develop very precise orbital models of the various planets, and to determine their respective masses and gravitational perturbations. Such measurements led to the discovery of the planets Uranus, Neptune, and (indirectly) Pluto. They also resulted in an erroneous assumption of a fictional planet Vulcan within the orbit of Mercury (but the explanation of the precession of Mercury's orbit by Einstein is considered one of the triumphs of his general relativity theory).